There is a growing interest today in products which have anti-microbial and anti-fungal properties. There are a number of additives, fibers and products on the market which claim to have these properties. However, many do not have such properties, or the properties do not remain for the life of the product, or they have adverse environmental consequences.
Various materials have been used in the past to provide anti-microbial and anti-fungal properties to fibers and fabrics.
Examples of some organic types of anti-microbial agents, are U.S. Pat. Nos.: 5,408,022 and 5,494,987 (an anti-microbial polymerizable composition containing an ethylenically unsaturated monomer, a specific one-, di- or tri-functional anti-microbial monomer and a polymerization initiator which can yield an unreleasable anti-microbial polymer from which the anti-microbial component is not released), U.S. Pat. No. 5,709,870 (a silver containing anti-microbial agent which comprises carboxymethylcellulose, a crosslinked compound, containing silver in the amount of 0.01 to 1% by weight and having a degree of substitution of carboxymethyl group of not less than 0.4 and the anti-microbial agent being a silver salt of carboxymethylcellulose, which is insoluble to water), U.S. Pat. No. 5,783,570 (an organic solvent-soluble mucopolysaccharide consisting of an ionic complex of at least one mucopolysaccharide and a quaternary phosphonium, an antibacterial antithrombogenic composition comprising organic solvent-soluble mucopolysaccharide and an organic polymer material, an antibacterial antithrombogenic composition comprising organic solvent-soluble mucopolysaccharide and an inorganic antibacterial agent, and to a medical material comprising organic solvent-soluble mucopolysaccharide).
Examples of some inorganic types of anti-microbial agents are:
Japanese Patent No. 1246204 (1988) which discloses an anti-microbial thermoplastic article with copper a compound added to the melted polymer just before extruding, in which the anti-microbial material is said to be resistant to washing.
U.S. Pat. No. 5,180,585 which discloses an antimicrobial with a first coating providing the antimicrobial properties and a second coating as a protective layer. A metal having antimicrobial properties is used including silver which is coated with a secondary protective layer.
Japanese Patent No. 2099606 (1990) which discloses a fiber with anti-microbial properties made of a liquid polyester and inorganic micro particles of zinc silicate, both being added to the melted polymer after polymerization and just before extrusion.
The use of anti-microbial agents in connection with thermoplastic material is known from U.S. Pat. No. 4,624,679 (1986). This patent is concerned with the degradation of anti-microbial agents during processing. This patent states that thermoplastic compounds which are candidates for treatment with anti-microbial agents include material such as polyamides (nylon 6 or 6,6), polyvinyl, polyolefins, polyurethanes, polyethylene terephthalate, styrene-butadiene rubbers.
Japanese Patent No. 2091009 (1990) and U.S. Pat. No. 5,047,448 disclose an anti-microbial thermoplastic polymer with copper or zinc compounds and fine particles of Al, Ag, Fe and Zn compounds and a liquid polyester, in which the anti-microbial material is said to be resistant to washing.
Japanese Patent No. 2169740 (1990) discloses a thermoplastic fiber such as PET which uses silver, copper or zinc as an anti-microbial agent. There is a cellulose component which reduces the amount of thermoplastic with anti-microbial agent and reduces the cost.
Examples of inorganic types of anti-microbial agent which have zeolite with silver is disclosed in U.S. Pat. Nos. 4,911,898, 5,094,847, 4,938,958 (use of zeolite with exchangeable ions such as silver and others), U.S. Pat. No. 5,244,667 (an anti-microbial composition which involves use of partial or complete substitution of ion-exchangeable metal ion such a silver, copper, zinc and others), U.S. Pat. No. 5,405,644 (an anti-microbial fiber having a silver containing inorganic microbiocide and the silver ion is stated to have been supported by zeolite, among other materials, the purpose being to prevent discoloration).
Various products have been made using anti-microbial fibers. U.S. Pat. No. 5,071,551 discloses a water purifier having a secondary filter downstream of its primary filter for removing microorganisms and antimicrobial means disposed between the two filters, use of an anti-microbial agent for a water purifier.
Japanese Patent No. 6116872 (1994) discloses a suede-like synthetic leather with an anti-microbial agent. It discloses the use of anti-microbial zeolite having an anti-microbial metal ion. It uses two fiber types and includes PET.
U.S. Pat. No. 5,733,949 discloses an anti-microbial adhesive composition for dental use. The composition was made by blending of a polymerizable monomer having alcoholic hydroxy group and water to a dental composition containing an anti-microbial polymerizable monomer and a polymerizable monomer having acidic group, and with a polymerization catalyst. Such composition has capability to improve adhesive strength between the tooth and the restorative material to prevent microbial invasion at the interface and kill microorganisms remaining in the microstructure.
U.S. Pat. No. 5,876,489 discloses a germ-removing filter with a filter substrate and an anti-microbial material dispersedly mixed into the filter substrate. The anti-microbial material is an ion exchange fiber bonded with silver ion. In the ion exchange fiber, silver ions capable of killing living germs through an ion exchange reaction.
U.S. Pat. No. 5,900,258 discloses a method for preventing a microorganism from growing and the breakdown of urea to ammonia on the surface of skin, wall, floor, countertop or wall covering, or in absorbent materials by incorporating an effective amount of naturally-occurring and/or synthetic zeolites. The absorbent materials are diapers, clothing, bedsheets, bedpads, surgical apparel, blankets, filters, filtering aids, wall coverings, countertops, and cutting boards, etc. Use of zeolite preventing bacterial infections and rashes in mammals may compromise cell wall processes including basic transport processes. Zeolites may capture or neutralize electrons and inhibit electron transport through key enzymes of the electron transport chain such as cytochrome oxidase.
U.S. Pat. No. 6,037,057 is for a bi-component fiber in which the cross sectional area of the sheath is less than 28% of the total cross sectional area. It also discloses the use of a slickening agent and use of an anti-microbial agent which is an inert inorganic particle having a first coating with the anti-microbial properties, and a second coating which has protective properties.
One of the disadvantages of some of the prior art is that the anti-microbial additives are organic and many organic materials either act as antibiotics and the bacteria “learns” to go around the compound, or many of them give off dioxins in use.
Also, many such additives are applied topically to the fibers or fabrics and tend to wash off or wear off over time and become ineffective. Also, by washing off the additives are placed into the waste water stream.
There are many patents and other published information which are available concerning garments and other articles intended for use for incontinent persons. Many of these deal with the problem of moving body fluids away from a person's skin to prevent the type of problems created when such fluids remain in contact with the skin for long periods of time, such as rashes and other skin eruptions. Absorbent layers are provided behind the layer which touches the skin.
However, there is the danger of infection due to bacterial and fungal growth in urine-soaked fabrics and the overall discomfort caused by wet clothing.
There has been little attention to a problem which remains even when the fluids are moved away from the skin. This is the problem caused by microbes which attach to the outer layer which touches the skin even when the fluids move into the absorbent layer. These microbes cause a variety of problems.
The University of Minnesota Extension Service, Waste Education Series published an article in 1998, “Infant Diapers and Incontinence Products: Choices for Families and Communities by Gahring et al relating to this subject (hereafter “UOM Article”). This article indicates that the use of disposable diapers and incontinence products have been widely adopted for babies and for adults with certain problems. There is an estimate that there are at least ten million adult Americans who are incontinent. One of the problems is rashes and skin irritation.
Moisture absorbing incontinence products are produced in various manners including plastic film or coated nylon for a waterproof backing, paper fiber, gelling material, or cotton gauze; flannel for a middle absorbent layer and nonwoven or woven or knitted fabrics made of polyester, olefin, viscose or cotton for the coverstock.
This article discusses health issues for babies relating to the condition of the skin and to the transmission of infectious diseases. Prolonged contact with urine and stool is a major cause of diaper rash.
There are environmental problems associated with the large use of disposable products of this type. And this will increase as the number of elderly people in our society increases. While disposables are placed into landfills together with other trash, it appears that many people do not empty the contents of disposables into the toilet, and a study has shown that diaper wastes represent a significant health hazard in landfills. While many such products claim to be biodegradable, this is not always correct and there is some difficulty in making the moisture impervious layers of the plastics used in such products, biodegradable.
Also it has been found that super-absorbent disposable diapers are more effective than cloth diapers with separate waterproof pants/wraps. The transmission of infectious disease is a major concern for care, outside of the home. The fecal containment of disposable diapers is found to be significantly better than that of cloth diapers with plastic pants.
Vehicle and aircraft cabin air filters are vulnerable to the seeding of bacteria and fungi from outside air sources and air conditioning systems, thus providing hospitable sites for their inhibited growth. The latter is especially true since these filters often recirculate cooled air from air-conditioners. Thus, these materials would benefit from having antibacterial and anti-fungal agents incorporated into them. However, most prior art approaches of coating fibers or materials with anti-microbial or anti-fungal agents have limited effect.
There have been complaints about the “musty air” smell which is notices when air conditioning equipment is turned on in such cabins. This smell is caused by the growth of mold and bacteria with the air conditioning system.
There exists a need to develop fabrics and other effective material for use in air filters for vehicle and aircraft cabins that do not cause the development of resistant bacterial strains. There also still exists a need for these filters to have substrates-anti-microbial agent systems that are resistant to being washed away, thus maintaining their potency as an integral part of the filters into which they are incorporated.
U.S. Pat. No. 5,876,489, mentioned above, describes use of a cation exchange to provide a fiber bonded with silver ions, usable in a germ removing filter for sterilizing air for a sterile room such as is used in the manufacture of food products. A problem with using silver zeolite fine particles for such a filter is that the particles fall out and generate dust, thereby deteriorating the function of a HEPA filter with which it is used. When other methods are used in which the zeolite particles are two microns, with fiber filament having a diameter of 8-15 microns, insufficient zeolite particles are available on the surface of the synthetic fiber filament.
Wound care dressings can introduce pathogens that increase the danger of infection due to bacterial and fungal growth into the wound tissue because it is necessary to changing these dressings frequently. As a result of the constant re-exposure of the healing wound to the air, the dressings used to cover these wounds are suitable for the use of anti-microbial and anti-fungal fibers during their manufacture. In addition, the use of these anti-microbial materials could allow these dressings to be used for longer periods of time before they need to be changed or even to possibly be reusable, although they are usually considered disposable after one use. However, most prior art approaches of coating such fibers or fabrics with anti-microbial or anti-fungal agents have had limited success.
Burn dressings are used to prevent infection due to high potential for introducing bacteria and other pathogens into the burn tissue due to the fact that the normal protective barrier of the skin has been grossly disrupted. The possibility of bacterial and fungal growth in the burn tissue during healing is one of the major dangers to recovery. Also, as a result of the constant re-exposure of the healing burn tissue to the air during the changing of dressings, the materials used to protect these burns are suitable for the use of anti-microbial and anti-fungal fibers during their manufacture. In addition, the use of these anti-microbial materials could allow these burn dressings to be used for longer periods of time before they need to be changed.
Several patents describe anti-microbial materials in which the anti-microbial agent is resistant to being washed away. Similarly, U.S. Pat. No. 4,919,998 (1990) discloses an anti-microbial medical fabric material for use in surgical gown and scrub suits, sterilization wrappers and similar material that retains its desirable properties after repeated institutional launderings.
U.S. Pat. No. 4,226,232 discloses a wound dressing which provides many desirable properties. However, there is only brief mention of the use of anti-microbial agents, and there is no discussion of providing such agents onto the surface of the fibers contacting the wound to provide the best efficacy of anti-microbial agents.
U.S. Pat. No. 5,098,417 for a cellulosic wound dressing with an active agent ionically absorbed thereon has the anti-microbial or anti-fungal agent applied to an already prepared fabric.
U.S. Pat. No. 5,147,339 for a dressing material for the treatment of wounds has an anti-microbial applied to the already formed fabric as a coating.
U.S. Pat. No. 5,219,325 for a wound dressing has a top layer and a lower layer (which contacts the wound) connected together by a fibrous layer. The lower layer has an anti-microbial applied after the layer is formed.
Thus, there still exists a need to develop metal-containing anti-microbial agents that do not cause the development of resistant bacterial strains for incorporation into fibers that are used to make a variety of materials. There also still exists a need for these anti-microbial agents to be resistant to being abraded or washed away, thus maintaining their potency as an integral part of the fibers into which they are incorporated.
PETG as used herein means an amorphous polyester of terephthalic acid and a mixture of predominately ethylene glycol and a lesser amount of 1,4-cyclohexanedimethanol. It is known that PETG can be used in polycarbonate blends to improve impact strength, transparency, processability, solvent resistance and environmental stress cracking resistance.
Udipi discloses in U.S. Pat. Nos. 5,104,934 and 5,187,228 that polymer blends consisting essentially of PC, PETG and a graft rubber composition, can be useful as thermoplastic injection molding resins.
Chen et al. in U.S. Pat. No. 5,106,897 discloses a method for improving the low temperature impact strength of a thermoplastic polyblend of PETG and SAN with no adverse effect on the polyblends clarity. The polyblends are useful in a wide variety of applications including low temperature applications.
Billovits et al. in U.S. Pat. No. 5,134,201 discloses that miscible blends of a thermoplastic methylol polyester and a linear, saturated polyester or co-polyester of aromatic dicarboxylic acid, such as PETG and PET, have improved clarity and exhibit an enhanced barrier to oxygen relative to PET and PETG.
Batdorf in U.S. Pat. No. 5,268,203 discloses a method of thermoforming thermoplastic substrates wherein an integral coating is formed on the thermoplastic substrate that is resistant to removal of the coating. The coating composition employs, in a solvent base, a pigment and a thermoplastic material compatible with the to-be-coated thermoplastic substrate. The thermoplastic material, in cooperation with the pigment, solvent and other components of the coating composition, are, after coating on the thermoplastic substrate, heated to a thermoforming temperature and the thermoplastic material is intimately fused to the thermoplastic substrate surface.
Ogoe et al. in U.S. Pat. No. 5,525,651 disclose that a blend of polycarbonate and chlorinated polyethylene has a desirable balance of impact and ignition resistance properties, and useful in the production of films, fibers, extruded sheets, multi-layer laminates, and the like.
Hanes in U.S. Pat. No. 5,756,578 discloses that a polymer blend comprising a monovinylarene/conjugated diene black copolymer, an amorphous poly(ethylene terephthalate), e.g. PETG, and a crystalline poly(ethylene terephthalate), e.g. PET, has a combination of good clarity, stiffness and toughness.
Eckart et al. in U.S. Pat. No. 5,958,539 disclose a novel thermoplastic article, typically in the form of sheet material, having a fabric comprising textile fibers embedded therein. The thermoplastic article is obtained by applying heat and pressure to a laminate comprising an upper sheet material, a fabric comprised of textile fibers and a lower sheet material. The upper and lower sheet materials are formed from a co-polyester, e.g. PETG. This thermoplastic article may be used in the construction industry as glazing for windows. One or both surface of the article may be textured during the formation of the articles.
Ellison in U.S. Pat. No. 5,985,079 discloses a flexible composite surfacing film for providing a substrate with desired surface characteristics and a method for producing this film. The film comprises a flexible temporary carrier film and a flexible transparent outer polymer clear coat layer releasably bonded to the temporary carrier film. A pigment base coat layer is adhered to the outer clear coat layer and is visible there through, and a thermo-formable backing layer is adhered to the pigmented base coat layer. The film is produced by extruding a molten transparent thermoplastic polymer and applying the polymer to a flexible temporary carrier thereby forming a continuous thin transparent film. The formed composite may be heated while the transparent thermoplastic polymer film is bonded to the flexible temporary carrier to evaporate the volatile liquid vehicle and form a pigment polymer layer. The heating step also molecularly relaxes the underlying film of transparent thermoplastic polymer to relieve any molecular orientation caused by the extrusion. Ellison also mentions that it is desirable to form the flexible temporary carrier from a material that can withstand the molten temperature of the transparent thermoplastic polymer. The preferred flexible temporary carriers used in his invention are PET and PETG.
Currently, many tee shirts, such as the grey athletic shirts, are made by blending in up to 10% of either solution dyed black polyester or stock dyed cotton. The solution dyed polyester has a disadvantage in that the product can no longer be labeled 100% cotton. The stock dyed cotton has the disadvantage in that it is not color fast, especially to bleach, and that it needs to be passed through a dye bath.
While anti-microbial agents are known in the footwear art, the agents used in these applications are generally organic substances. The disadvantage of these organic agents when used as anti-microbial agents is that bacteria can develop a resistance to their action. Thus, one is faced with the emergence of bacterial strains that are no longer affected by these anti-microbial agents which negates the function of these materials, and is harmful to humans since they are resistant to antibiotics.
One type of known shoe component is an insole disclosed in U.S. Pat. No. 4,864,740 for Disposable Insoles, which includes three layers in which the anti-microbial agent is placed into the middle layer. As an alternative, the anti-microbial can be placed into the other layers, disclosing that the particular layer into which the anti-microbial agent is used is not important.
U.S. Pat. No. 4,401,770 for Shoe Insole Having Anti-bacterial and Anti-fungal Properties is a flexible polyurethane foam prepared from a reaction mixture incorporating an anti-bacterial and anti-fungal agent which is a pyridinethione compound. The agent is introduced into the product and is the same concentration throughout the product.
Thus, there still exists a need to develop anti-microbial footwear components that do not cause the development of resistant bacterial strains. There also still exists a need for these components to have anti-microbial agent systems that are resistant to being worn away by abrasion, thus maintaining their potency as an integral part of the footwear components into which they are incorporated.
Sheet materials for various uses are vulnerable to the seeding of bacteria and fungi from various sources, thus providing hospitable sites for their uninhibited growth. The latter is especially true since, depending upon the end use, they often are used in environments where there is great exposure to microbes and fungi. One example is cafeteria trays. Thus, these materials would benefit from having antibacterial and anti-fungal agents incorporated onto them and/or into them. However, most prior art approaches of providing sheet materials with anti-microbial or anti-fungal agents have limited effect.
A variety of patents relate to anti-microbial materials being added to materials. For example, U.S. Pat. No. 3,959,556 (1976) relates to synthetic fibers that incorporate an anti-microbial agent. U.S. Pat. No. 4,624,679 (1986), mentioned above, uses anti-microbial agents in connection with thermoplastic materials. These materials are formed by mixing polyamide resins, anti-microbial agents, and an antioxidant for reducing the degradation of the anti-microbial agent at the high temperatures necessary for processing.
Several other patents describe anti-microbial materials in which the anti-microbial agent is resistant to being washed away. U.S. Pat. No. 4,919,998 (1990) discloses an anti-microbial material that retains its desirable properties after repeated washings.
However, these materials have two inherent commercial disadvantages. First, while the anti-microbial agents incorporated into them do show some resistance to repeated washings, these agents do leach out of the materials, primarily because they are not physically incorporated into them. In fact, in many cases, the anti-microbial agents are only loosely bound into the material and are relatively easily washed away or naturally abraded away over time.
On the other hand if the agents are buried too deeply in the material or homogeneously distributed they will not contact microbes at all and the economics of usage will be adversely affected.
Second, the anti-microbial agents used in these applications are generally organic substances. The disadvantage of these agents when used as anti-microbial agents is that bacteria can develop a resistance to their action. Thus, one is faced with the emergence of bacterial strains that are no longer affected by these anti-microbial agents which negates the function of these materials.
U.S. Pat. No. 4,923,914 for a Surface-Segregatable, Melt-Extrudable Thermoplastic Composition discloses forming a fiber or film of polymer and an additive in which the additive concentration is greater at the surface, for example when surfactants are added to polymers to impart a special property thereto such as a hydrophilic character to the surface, if the additive is compatible with the polymer there is a uniform concentration of the additive throughout the polymer. In the past such webs have been bloomed to bring the surfactant to the surface. But the surfactant is incompatible at melt-extrusion temperatures. The patentee describes a process for overcoming this problem.
However, the process described has not been very usable with anti-microbial agents. For example, see U.S. Pat. No. 5,280,167 which describes the '914 patent discussed above and states that previous attempts to apply the teachings thereof to the preparation of non-woven webs having anti-microbial activity were not successful. This '167 patent provides for delayed anti-microbial activity in order to delay the segregation characteristic of the '914 patent from occurring. The additive which is used is a siloxane quaternary ammonium salt, an organic material.
While these anti-microbial agents are designed to prevent the development of resistant bacterial strains, the use of metal-containing materials presents the added difficulty of being able to successfully disperse the anti-microbial agents throughout the material. Since these metal-containing compounds exists as fairly large size particles (10 microns and greater), the ability to evenly mix or distribute them is limited. In addition, because of this size problem, these substances must necessarily be applied to the surfaces of materials instead of being incorporated into them. The latter causes the additional disadvantage of making the applied anti-microbial agents relatively labile to washings or abrasion.
Thus, there still exists a need to develop anti-microbial non-woven sheet material and fabrics for various uses that do not cause the development of resistant bacterial strains. There also still exists a need for these filters to have substrates-anti-microbial agent systems that are resistant to being washed away, thus maintaining their potency as an integral part of the filters into which they are incorporated.
U.S. Pat. No. 4,350,732 for reinforcing laminate which issued Sep. 21, 1982 discusses a moldable laminate which could be molded into curved shapes and which is bondable to a carrier surface and which is useful in the making of military boots and the like. The present invention is an improvement.
Institutional furnishings are subject to excessive wear and tear. These furnishings must withstand the constant onslaught of dirt and spills of a variety of substances. They must also stand up to frequent cleanings with industrial strength cleansers. As a result, these furnishings could be made stronger and more resistant by using anti-microbial and anti-fungal agents in their manufacture. The limited prior art approaches of coating fibers and/or fabrics with anti-microbial or anti-fungal materials have had only limited success.
Home furnishings are not subjected to as much wear and tear as institutional furnishings and are usually made of a material which has a softer “feel” and is usually more delicate than those made for institutional use. Therefore, it is difficult to make such materials which will stand up to repeated washings and to wear, particularly when they have been prepared with additives for special properties such as anti-microbial agents.
U.S. Pat. No. 3,983,061 for a process for the permanent finishing of fiber materials, including carpets, discloses an aqueous acid liquid for finishing fiber materials especially dyed carpets to make them anti-static, dirt-repellent, and optionally anti-microbial using a single bath process for finishing dyed textile floor coverings to make provide these characteristics to them. It states that the properties are “permanent” and defines this to mean retaining the properties after a “prolonged” period of wear and tear. However, the anti-microbial properties are not believed to last sufficiently long to be of commercially useful application, and the anti-microbial agent disclosed is organic in nature.
U.S. Pat. No. 4,371,577 for an anti-microbial carpet containing amino acid type surfactant is incorporated into fibrous materials prior to or after fabrication into a carpet using an organic material. The fibrous materials can be polyamide acrylic, polyester or polypropylene fibers. The preparation is accomplished in two manners. The first is that the pile yarns, the carpet foundations or the yarns for carpet foundation are subjected to the impregnation treatment with a surfactant, and the other is that a carpet fabricated from fibrous materials is impregnated with an organic material.
U.S. Pat. No. 5,762,650 for a biocide plus surfactant for protecting carpets where the dyeing and anti-microbial finishing is performed simultaneously. The anti-microbial agent is an organic material.
While there are known anti-microbial agents which are said to be designed to prevent the development of resistant bacterial strains, the use of metal-containing materials presents the added difficulty of being able to successfully disperse the anti-microbial agents throughout the fibers. Since these metal-containing compounds exist as fairly large size particles (10 microns and greater), the ability to evenly mix or distribute them is limited. In addition, because of this size problem, these substances must necessarily be applied to the fibers instead of being incorporated into them. The latter causes the additional disadvantage of making the applied anti-microbial agents relatively labile to washings.
Thus, there still exists a need to develop fabrics, materials and surfaces substrates for use in home and institutional furnishings which contain metal-containing anti-microbial agents that do not cause the development of resistant bacterial strains for incorporation into fibers that are used to make a variety of fabrics. There also still exists a need for these anti-microbial agents to be resistant to being washed away, thus maintaining their potency as an integral part of the fibers, fabrics, materials, and furnishings into which they are incorporated.
Medical wipes are used for a variety of cleaning and disinfectant purposes in hospital and other institutional settings. Even though most current materials of this kind are disposable, their use increases the potential of moving pathogens from surface to surface. Any spreading of these pathogens increases the possibility of bacterial and fungal growth on a variety of surfaces, which can lead to the transmission of infectious materials, particularly in institutional settings. Thus, the materials used in medical wipes are amenable to the incorporation of anti-microbial and anti-fungal fibers during their manufacture. By using these anti-microbial materials, medical wipes could be used for longer periods of time before they need to be changed. However, most prior art approaches of coating fibers or fabrics with anti-microbial or anti-fungal agents have had limited success.
U.S. Pat. No. 5,709,870 (1998), mentioned above, discloses a silver-containing anti-microbial agent that has good affinity to the fiber and is stable to heat and light. The anti-microbial consists of silver bound to carboxymethylcellulose in the amount of 0.01 to 1.0 percent silver by weight that is applied to the fibers.
While these anti-microbial agents are designed to prevent the development of resistant bacterial strains, the use of metal-containing materials presents the added difficulty of being able to successfully disperse the anti-microbial agents throughout the fibers. Since these metal-containing compounds exists as fairly large size particles (10 microns and greater), the ability to evenly mix or distribute them is limited. In addition, because of this size problem, these substances must necessarily be applied to the fibers instead of being incorporated into them. The latter causes the additional disadvantage of making the applied anti-microbial agents relatively labile to washings.
Thus, there still exists a need to develop metal-containing anti-microbial agents that do not cause the development of resistant bacterial strains for incorporation into fibers that are used to make a variety of materials. There also still exists a need for these anti-microbial agents to be resistant to being abraded away, thus maintaining their potency as an integral part of the fibers into which they are incorporated. In the event they are not disposable, they need to be resistant to washings.